1. Field of the Invention
The present invention relates to a silicone composition that can be crosslinked into elastomer and to a process using the composition according to the invention for forming seals for leakproofing and for assembling the components of a powertrain. Silicone elastomers prepared from the composition according to the invention have:                good mechanical strength properties such as the shore hardness, the breaking strength, the modulus at 100% elongation, and        good resistance to aging in chemically corrosive fluids such as those used, for example, in a powertrain, namely engine oils, gearbox and powered axle lubricants, oil/fuel mixtures, cooling liquids, fuels or antifreeze liquids, and        good properties of adhesion even to surfaces polluted with oils used in a powertrain.        
2. Description of Related Art
The term “cooling liquid” means any heat-exchange liquid used for evacuating heat from a mechanical or electronic system.
Silicone compositions that can be crosslinked into elastomer to form leakproofing seals are known. Specifically, they are suitable in particular for forming in-situ leakproofing seals, which are formed directly during the assembly of the elements, in particular in the motor vehicle sector.
Among the silicone compositions that can be crosslinked into elastomer which are known for this type of application, those that crosslink at room temperature form a category that is particularly appealing since they do not require the installation of an energy-consuming oven.
These silicone compositions are classified into two different groups: one-pack compositions (RTV-1) and two-pack compositions (RTV-2). The term “RTV” is the abbreviation for “room-temperature vulcanizing”.
During crosslinking, water (either provided by atmospheric moisture in the case of RTV-1 compositions, or introduced into one part of the composition in the case of RTV-2 compositions) enables the polycondensation reaction, which results in the formation of the elastomeric network.
Generally, one-pack compositions (RTV-1) crosslink when they are exposed to atmospheric moisture. Usually, the polycondensation reaction kinetics are extremely slow; these reactions are thus catalyzed with a suitable catalyst.
Furthermore, in the face of a transport industry that is undergoing great changes, new constraints are arising linked to increasing engine yields, increasing operating temperatures, reducing fuel consumption and reducing the frequency of maintenance.
Thus, formulators of powertrain fluids (engine oil, gearbox and powered axle lubricant, oil/fuel mixture, cooling liquid, fuel or antifreeze liquid) continue to improve the performance qualities of these products by adding increasingly efficient additives. The amount of additives incorporated into these products is incessantly increasing, which has the effect of increasing their chemical corrosiveness toward the flexible members, for example leakproofing seals, present in the devices in which these products are used.
Patent application JP-A-2009/197188 describes silicone compositions which have good resistance on contact with the various fluids used in a powertrain, but these compositions comprise complex and expensive crosslinkable oils which contain a C1 to C5 alkylene joint represented by the symbol Y in the following formulae:

Patent application EP 2 151 480 describes silicone compositions which have good resistance on contact with the various fluids used in a powertrain, but these compositions comprise, inter alia, a surface-treated calcium carbonate.
Patent application PCT/FR 2012/000 364 describes silicone compositions which have good resistance on contact with the various fluids used in a powertrain, but these compositions comprise an amount strictly greater than 35% by weight, relative to the total amount of the composition, of at least one ground natural calcium carbonate with a specific surface area strictly less than 3 m2/g, measured according to the BET method, and which has been surface-treated with at least one compound chosen from the group consisting of a paraffin, a fatty acid, a fatty acid salt, and a mixture thereof.
U.S. Pat. No. 5,641,832 describes silicone compositions which have good resistance on contact with the various fluids used in a powertrain, but these compositions comprise a filler prepared by impregnation of a porous filler with a volatile organic compound that is incompatible or partially incompatible with the polyorganosiloxane used.
Patent application WO 2011/114 021 describes silicone compositions which have good resistance on contact with the various fluids used in a powertrain, but these compositions comprise at least one siloxane which is a condensate obtained by partial hydrolysis and condensation of a polyalkoxylated silane, said siloxane containing from 2 to 10 identical or different siloxyl units, of formula:(R2)x′(OR3)y′SiO[4−(x′+y)]/2                 in which:                    x′=0, 1, 2 or 3; y′=0, 1, 2 or 3, x′+y′=0, 1, 2 or 3,            the symbol R2 represents a C1 to C13 monovalent hydrocarbon-based radical, and            the symbol R2 represents a C1 to C6 monovalent hydrocarbon-based radical or an alkoxyalkyl radical optionally comprising an ester function, and            with the condition that for at least one siloxyl unit, the index y′ is ≧1.                        
These compositions have the drawbacks of leading, after their aging, to elastomers whose mechanical properties and properties of resistance to engine oils and adhesion to a polluted surface are degraded.
There is thus an increasing need to find novel silicone compositions that are useful for forming seals for leakproofing and for assembling the components of a powertrain, even on surfaces polluted with oils, and even after aging of these novel compositions.